This invention relates to a goggle and lens for use with a film advance system to improve overall performance.
Goggles which are intended for off-road use such as by motorcycle riders and racers have included a film advance system attachable to the goggle. A transparent film extends from a supply magazine at one side of the goggle and across the lens to a take-up magazine at the other side. A drive mechanism in the take-up magazine can be activated to move the film across the goggle lens when dirtied such as by mud in order to provide a clear field of view for the wearer. One example of such a system using a mechanical drive mechanism is illustrated in Smith U.S. Pat. No. 4,428,081. In this system, the film advance mechanism is formed by a mechanical actuator which is activated by manually pulling a knob attached to a flexible cord. Also known is an electric drive in which the film is advanced by an electric motor powered by a battery, an example of which is the EFS (Electronic Film System) previously sold by Scott USA, the assignee of the present application.
While such goggle and film advance systems have performed satisfactorily in generally dry conditions, the presence of moisture in mud or due to rain can substantially degrade the performance of the system. Initially, any water which strikes the lens and transparent film will act as a lubricant and there is no difficulty in advancing the film to its next position. As the film is advanced, however, the water film is reduced and surface tension begins to significantly increase the amount of force needed to advance the transparent film. Off-road motorcycle riders who wear such goggle system have experienced a significant increase in the amount of force needed to advance the film to the point of a lock-up condition, where the goggle can be pulled off the wearer""s head in the case of a mechanical advance mechanism, or an inability of the electrical drive system to advance the film. At other times, the transparent film can exhibit some intermittent sticking, followed by release, but this condition can lead eventually to a lock-up condition.
Various attempts have been made to obviate the problems created by liquid entering the interface region between the goggle lens and the moveable transparent film. As shown in the Smith U.S. Pat. No. 4,428,081, it has been known to attach a C-shaped channel formed of transparent material horizontally across the lens which formed a slot for restraining the edge of the film, and also provide a pair of upstanding ribs formed of transparent material and attached to the lens near the bottom of the moveable film in an attempt to create elongated liquid barriers to prevent the entry of liquid due to surface tension. Another approach has been a xe2x80x9cnon-stick lensxe2x80x9d which has been sold by the present assignee Scott USA and which consists of a replacement main lens having a plurality of protrusions or ribs formed in the lens to raise the film above the main lens. In addition, some racers have custom modified their goggle and film advance systems by locating a transparent monofilament fishing line diagonally across the lens and secured with screws into the lens in order to lift the transparent film off the goggle lens and break surface tension caused by moisture. Still other racers have placed a slippery material such as baby powder between the outer surface of the main lens and the moveable film in yet another attempt to break the surface friction which can form when the lens becomes wet.
Despite these various approaches, none have proved entirely satisfactory. There is a need for a permanent solution which does not wear off during use. Very importantly, the structural integrity of the main lens should be maintained. Any structure formed in the lens material or attachment screws or the like can weaken the main lens and/or the protective hard coating of the main lens. Molded-in or pressed indentations and/or sharp corners in a lens can create hairline cracks or crazing which can break the hard coating or create stress concentrations and lead to degradation of the lens. Furthermore, any solution should be cost effective and cause minimal disruption to existing manufacturing processes, and therefore should be adaptable for use with existing main lenses formed of polycarbonate having a hard coating without causing long-term degradation or loss of any integrity of the lens.
A unique goggle, lens and film advance system is provided which overcomes the above problems and disadvantages of prior goggle systems, particularly when used in wet or heavy moisture conditions. A matrix or grid of projections are attached to an external surface of the main lens and create a bumped surface which extends above the main lens in a field of view region to lift the transparent film away from the otherwise smooth lens surface. The grid pattern which results does not weaken the structural integrity of a hard coated plastic lens having impact resistance.
In one form, the plurality of projections are formed by transparent ink drops or raised dots which are built up by silk screen printing using multiple passes over the goggle lens. The screen inks provide good adhesion to a polycarbonate lens having a hard coating, and permit the projections to be built rapidly to an acceptable height. Furthermore, the screen ink projections are desirably formed using a transparent material and are of minimal visual obstruction despite locations in front of the wearer""s eyes.
The main lens when printed with a pattern of transparent ink droplets has utility by itself as a replacement lens for use with existing goggle and film advance systems, or can be provided as a film advance subsystem, as well as creating in combination an improved goggle and film advance system.
A better understanding the present invention along with other objects and advantages will become apparent in the following description and with reference to the following drawings.